1. Field of the Invention
The present invention relates to an apparatus for tracking an overhead line for the use of maintenance/inspecting of overhead lines such as a high-voltage power line and an overhead cable.
2. Description of the Related Art
Conventionally, the points to be repaired of the overhead line are visually found by a patrol-man riding on a helicopter or an automobile for instance, and then repaired by a serviceman coming from the ground.
In another method, a wire rope used for a ropeway or a ski lift is stretched alongside the overhead line, with a maintenance/inspecting apparatus being slung by means of a support arm over the wire rope and transferred by hauling the rope.
The former method, however, had a disadvantage that accurate checking is difficult due to the partial observation from only one direction as well as the long distance from the helicopter or automobile to the overhead line. On the other hand, the latter had a drawback that it required an enormous cost of construction and is uneconomical owing to the wire rope to be stretched alongside the overhead line.
Therefore, in order to solve this problem, there has been conceived a self-running maintenance/inspecting apparatus which is capable of unmanned travel on the overhead line.
The self-running maintenance/inspecting apparatus has a traction unit with a pair of moving wheels which is slung over the overhead line. In this case, the traction unit is movable with the overhead line being clamped between the moving wheels and clamp wheel located below the moving wheels. To the traction unit, is coupled a defect detection unit which is mounted with a sensor and a recording device thereon so as to inspect the overhead line.
A tower usually supporting the overhead line such as a power line, is disadvantageously an obstacle to the damper or counterweight of the self-running maintenance/inspecting apparatus. However the apparatus could not detour around the tower since it is moved with the overhead line being clamped between the moving wheels and clamp wheel. It was also impossible for the apparatus to climb over the cable holding metal fittings such as strain insulators and clamps attached to the overhead line. Consequently the above-mentioned self-running maintenance/inspecting apparatus required complicated work such as sling-change of the tracking apparatus every short section of line, thereby deteriorating the maintenance/inspecting work efficiency.